Heat stabilizer for polymers of



mill.

- Patented May 25, 1943 -11mm srABmIzEn FOR POLYMERS or VINYL onnomna Winfield Scott, Akron, Ohio, assignor to Wingroot Corporation, Wilmington, Del... a corporation Delaware No carving. Application April 1, ion.

- Serial No. scans '3 (llalms.

This invention relates to a method of improving the stability of polymeric masses and articles made therefrom against the efiect of heat.

Polymers of various types, while substantially clear when freshly made, often undergo discoloration and deterioration from heat, such as that employed in molding and processing these polymeric masses to form useful articles; Various substances have been added to the polymers to retard or prevent such discoloration and darkening but not always with fully satisfactory etiects.

it has now been found that masses resulting from the polymerization of monomers which include or comprise vinyl chloride may be heatstabilized by the addition to the mass alter polymerization of a small amount of a metal imide or amide. This is especially true of the phthalimides and the sulr'onamides of the alkali metals, alkaline earth metals and lead, the term phthalimide being employed to cover not only the nuclear-unsubstituted compound but also those in which the nucleus carries substituents, such as alhyl, chlorine, bromine, etc. and the term sulionamide being employed to cover this class, including benzene, toluene and naphthalene sulionamides and the like. Preferably, there is employed one of the following: sodium phthalimide, potassium phthalimide, lithium phthalimide, barium phthalimide, magnesium phthalimide, lead phthalimide, sodium sulfonamide, sodium p-toluene sulionamide, barium p-toluene sulionamide, barium naphthalene sulfonamide, magneslum p-toluene sulfonamide, magnesium sullenamide, lead sulionamide, lead p-toluene sulfonamide and lead naphthalene sulfonamide. Barium phthalimide and barium p-toluene sulfonamide are particularly effective. The compounds of any of the foregoing metals and hormone sulionamide, naphthyl sulfonamide and nuclear substituted chloro or bromo phthalimide may also be used.

in order to test the stabilizing effect of the foregoing compounds, they were incorporated in aiormula consisting of we parts of a copolymer of sea, vinyl chloride and 15% vinylidene chloride, at parts of tricresyl phosphate, and 3 parts oi one of the foregoing heat stabilizers. The copolymer, the plasticizer and the stabilizer were intimately mixed and then placed on a hot rubber After mixing until uniform, the product was sheeted off the mill.

Test sheets were then made by heating samies oi the formula in a mold to produce a block i" square and in thickness. The effective- (Cl. Edit-$6) ness of the heat stabilizer was observed by noting with other copolymers containing vinyl chloride.

Thus, copolymers of vinyl chloride and one of the following: butadiene, acrylonitrile, methacrylonitrile, styrene, vinyl bromide, isoprene, vinyl esters of carboiiylic acids, such as vinyl acetate, esters of acrylic and substituted acrylic acids, such as methyl and ethyl acrylates and methacrylates, may also be heat stabilized by the incorporation of one of the substances herein set forth or other substances of the same class, i. e., amides and imides, particularly phthalimides and sulronamides, oi the alkali metal and alkaline earth metal groups and lead.

While there have been described above the preferred embodiments of the invention, it will be apparent to those skilled in the art that various modifications and changes may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

The use of the sulionamides is covered in my divisional application Serial No. 436,319, filed March 26, 31942.

1. A method of heat-stabilizing polymerized masses containing a polymer of vinyl chloride which comprises adding to the polymer one of the group consisting of the alkali metal, the alkaline earth metal and the lead phthalimides.

2. A method of heat-stabilizing masses result ing from the polymerization of monomers comprising vinyl chloride which is characterized by adding to the polymer one of the group consisting of the alkali metal, the alkaline earth metal and the lead phthalimides.

3. A method of heat-stabilizing copolymers of vinyl chloride and vinylidene chloride which comv prises adding to the copolymer one of the group consisting of the alkali metal, the alkaline earth metal and the lead phthalimides.

l. A method of heat-stabilizing masses resulting from the polymerization of monomers com-.

prising vinyl chloride which is characterized by adding to the polymer an alkaline earth phthalimide.

5. A method of heat-stabilizing masses resulting from the polymerization of monomers comprising vinyl chloride which is characterized by adding to the polymer 8. lead phthalimide.

6. A method of heat-stabilizing masses resulting from the polymerization of monomers comprising vinyl chloride which is characterized by adding to the polymer barium phthalimide.

7. A method 0! heat-stabilizing masses resulting from the polymerization of monomers comprising vinyl chloride which is characterized by adding to the polymer lead phthalimide.

WINFIELD SCOTT. 

